The present invention relates to subterranean treatments, and more particularly, to water-based polymers as friction reducers in aqueous treatment fluids and associated methods.
During the drilling, completion, and stimulation of subterranean wells, aqueous treatment fluids are often pumped through tubular goods (e.g., pipes, coiled tubing, etc.). A considerable amount of energy may be lost due to friction between the aqueous treatment fluid in turbulent flow and the formation and/or tubular goods located within the well bore. As a result of these energy losses, additional horsepower may be necessary to achieve the desired treatment. To reduce these energy losses, friction reducing polymers have heretofore been included in aqueous treatment fluids. The use of friction reducing polymers should reduce the frictional losses due to friction between the aqueous treatment fluid in turbulent flow and the tubular goods and/or the formation.
An example of a stimulation operation that may utilize friction reducing polymers is hydraulic fracturing. Hydraulic fracturing is a process commonly used to increase the flow of desirable fluids, such as oil and gas, from a portion of a subterranean formation. In hydraulic fracturing, a fracturing fluid is introduced into a subterranean formation at or above a pressure sufficient to create or enhance one or more factures in the formation. Enhancing a fracture includes enlarging a pre-existing fracture in the formation. To reduce frictional energy losses between the fracturing fluid and/or the formation, friction reducing polymers may be included in the fracturing fluid. One type of hydraulic fracturing that may utilize friction reducing polymers is commonly referred to as “high-rate water fracturing.” Unlike conventional fracturing fluids, fluids used in high-rate water fracturing generally do not contain a sufficient amount of a water-soluble polymer to form a gel. Gel formation is based on a number of factors including the particular polymer and concentration thereof, temperature, and a variety of other factors known to those of ordinary skill in the art. As a result, the fracturing fluids used in these high-rate water fracturing operations generally have a lower viscosity than traditional fracturing fluids. Additionally, while fluids used in high rate water fracturing may contain a friction reducing polymer, the friction reducing polymer is generally included in the fracturing fluid in an amount sufficient to provide the desired friction reduction without forming a gel.
However, the use of friction reducing polymers has proved challenging from an environment standpoint. For example, many of the friction reducing polymers that have been used previously are provided as oil-external emulsion polymers, wherein upon addition to the aqueous treatment fluid, the emulsion should invert releasing the friction reducing polymer into the fluid. The hydrocarbon carrier fluid present in the oil-external emulsion may pose environmental problems with the subsequent disposal of the treatment fluid. Among other reasons, disposal of hydrocarbons (e.g., such as the carrier fluid in the oil-external emulsion) may have undesirable environmental characteristics and/or may be limited by strict environmental regulations in certain areas of the world. Furthermore, the hydrocarbon carrier fluid present in the oil-external emulsion also may undesirably contaminate water in the formation.